Spark-plug.



S. N. MCCLEAN.

SPARK PLUG.

APPLICATION FILED AUG-5.1912.

Patented May 2, 1916.

UNITED STATES PATENT OFFICE.

SAMUEL N. MccLnAN mama COMPANY,

OF DETROIT, MICHIGAN, ASSIGNOR T0 MCCLEAN, SPERLIGH 86 01'! DETROIT, MICHIGAN, A PARTNERSHIP COMPOSED 0F SAID MCCLEAN, H. H. SPERLIGH, AND J. H. UHLIG.

SPARK-PLUG.

Specification of Letters Patent Application filed August 5, 1912. Serial No. 713,356.

To all whom it may concern:

Be it known that I, SAMUEL N. MCCLEAN, a citizen of the United States of America, residing at No. 204 Hancock avenue East, in the city of Detroit and county of Wayne, State of Michigan, have invented certain new and useful Improvements in Spark- Plugs, of which the following is a specification, reference being had therein to the accompanying drawings.

The invention consists in a spark plug comprising an insulation carrying the inner electrode and a casing cast on the insulation and carrying or forming the outer electrode; all as more fully hereinafter described and particularly pointed out in the claims.

In the drawings: Figure 1 is a vertical central longitudinal section through a spark plug embodying my invention, through the die in which the casing is cast and showing .the plug therein; and Fig. 2 is a section on line aa, showing plan.

In the present state of the art, spark plugs for gas engines are ordinarily made by forming a central porcelain insulation through which the inner electrode passes and is secured and an outer metallic casing adapted to be screwed into the cylinderhead, with a suitable wrench-hold and with various devices for securing the casing and the insulation together in such a way as to form a tight joint between the two, so as to prevent the leakage of the gases and still not break the porcelain. These devices as ordinarily used embody one or more gaskets or packings, a bushing and various clamping devices, and one or more nuts and lock-nuts and lock-washers, requiring a considerable expense in the manufacture of the casing and of the plug itself upon which the screwthreads are cut, both for engagement with the engine cylinder and for the clamping bushing. It has also been proposed to make the top of the plug in spark plugs by making the outer casing in either separate the insulation from the casing or break the latter.

My invention is intended to overcome the difficulties of these prior constructions, to simplify and cheapen the cost of manufacture and to produce a more reliable and efficient spark plug than those heretofore made.

In making my spark follows: A represents is preferably of plug I proceed as the insulation, which porcelain or similar material, which may be of the ordinary construction but which I prefer to construct as shown in Fig. 1 in which the outer surface of the insulation is provided with oppositely-tapering conical faces a and b, meeting at the point 0, which point is preferably opposite the wrench-hold d of the casing B. v In the insulation I place the usual electrode (J, which may be secured therein in any suitable manner and is provided, as usual, at its outer end with any desired head, as D, to which the wires may be connected. This insulation is placed in suitable dies; in this case I have illustrated a metal die consisting of the two parts E and F, having the lower cavity G in which the lower portion of the porcelain will fit; and I also show a sleeve H screwed into the upper end and having a bearing upon the upper tapering portion a of the porcelain, to hold the porcelain tightly in position in the mold cavity. I represents the sprue through which the metal may be poured. The moldcavity has an enlarged portion, J, preferably of hexagonal shape, or any other shape suitable to produce a wrench-hold, and the lower cylindrical portion K. has screw-' threads therein, forming the nipple which is to be screwed into the engine-head. It will thus be seen that there is, in this construction, a portion of the metal ofthe casing both above and below the shoulder C and, as above described, this shoulder, or the tapering portions, are opposite the hex- Patented May 2, 1916. I

agonal or squared portion of the plug. The I parts being thus constructed, I pour or force the metal through the sprue I into the mold cavity and cast the metal upon the insulation, allowing the same to remain until it is set, so that there is formed about and upon the insulation the casing, with its is poured around the insulation cools it contracts and tightens upon the insulation. I get the best results, by having the thickest metal at the wrench-hold, opposite the point Where the oppositely-inclined cones meet. By casting the metal upon these oppositely inclined surfaces I securely fasten the insulation in the casing and do away with the necessity of lock-nuts, gaskets, and other devices common in the commercial spark-plug.

In casting the casing I prefer to use alloys of low or medium fusing point, suchas of aluminum, zinc, tin and copper, as commonly used in die casting. The plug thus constructed, when removed from the die, it complete and ready for use, with screwthreads and wrench-hold, and the casing is seated upon the porcelain and secured there to not only by the casting operation but also by the shrinkage, so as to make a perfectly formed contact on the varying surfaces of the porcelain, at all points; thus avoiding the use of gaskets, bushings, packings, etc., which, heretofore, it has been found necessary to use in spark-plugs to prevent difficulties arising from accumulation of soot, oil, carbon, dirt, gases, and other conditions.

What I claim as my invention is:

1. A spark plug, comprising an insulator core, an inner electrode therein and an outer casing adapted for engagement with an engine cylinder and within which said core is arranged, said casing being cast upon said core and shrunk thereupon to'form a gas-tight joint therewith.

2. A spark-plug, comprising an insulator core having an enlarged intermediate portion and an outer casing within which said core is arranged embracing said intermediate portion and in contact therewith on op-.

posite sides of said enlargement, said casing being cast upon said insulating core and shrunk thereupon to form a gas-tight joint with said enlargement upon both sides thereof.

3. A spark plug, comprising an insulator core, an inner electrode therein, an outer casing within which said core is arranged, there being abutting shoulders, upon, said casing and core, and said casing being cast upon said core and shrunk thereupon to form a gas-tight joint between said shoulders.

In testimony whereof I aflix my signature in presence of two witnesses.

SAMUEL N. MCCLEAN.

Witnesses:

JAMES P. BARRY, ADELAIDE I. AnAMs. 

